It is well known to provide spacers in order to define the spacing between the panes of isolating glazings consisting of a plurality of parallel glass panes spaced by an isolating cavity.
A plurality of such spacers made of different materials and of different shapes is known in the art. Spacers made by roll forming of a metal foil are widely used in the art and considered to be one of the preferred alternatives because of their stability and their low gas diffusion properties.
Insulating Glass Units (IG units) having a plurality of glass panes are made by automatic manufacturing machines. Spacers are automatically bent to the desired size and shape and are arranged between two neighbouring glass panes. Spacers made of metal foils can be easily bent and will remain in the bent position.
Furthermore, spacers made of metal foils have a high resistance against diffusion of gases and moisture penetration. Within the space between the neighbouring glass panes, there is arranged a gas, for instance argon having good isolating properties. In order to avoid any loss of gas, the spacers delimiting the cavity need to be resistant against diffusion of such gaseous elements.
However, known spacers which are exclusively made of metal such as aluminium and galvanized steel have also some disadvantages. Due to a relatively high heat conductivity of metal, spacers made of a metal foil still have a heat conductivity which under certain circumstances may be too high.
In order to further reduce the heat conductivity, it has been suggested to use plastic material for forming such spacers. Plastic material has, however, relatively high gas diffusion as compared to metal. It thus has been suggested to provide a metal foil over a plastic body. Such a spacer is e.g. shown in EP 852 280.
A further problem of spacers made of plastic material is their instability during the manufacturing process. In particular, a spacer bent to the desired frame shape may be slightly deformed during assembly because of the resiliency of plastic material. Misalignments of the spacer during manufacturing thus are possible. In order to avoid this problem, it has been suggested to use glass fibre reinforced plastic material in EP 852 280. Furthermore, plastics spacers including stabilising material in a plastic body have been proposed e.g. in WO 99/15753 or in WO 99/41481. However, these solutions have also some disadvantages. In particular, manufacturing is relatively complicated.
Similar spacers made from a body of plastic material are further known from DE 9 214 799, EP 1 022 424, EP 947 659 A2, EP 1 233 136 A1, WO 99/42693 or WO 03/074830. In U.S. Pat. No. 5,630,306 there is disclosed an insulating spacer which comprises a main body formed of a plastic material. Metallic leg members are attached to the plastic main body. While the problem of heat conduction and diffusion can be addressed with such spacer, some problems remain in context with bending the spacer into the desired frame shape and later during assembly of an IG Unit. In particular, the lateral legs may be deformed during bending out of their plane so that an irregular shape may result. Such an irregular shape is particularly disadvantageous if a sealing contact between the spacer and a glass pane shall be achieved.
Another way of making spacers with a low heat conductivity could be by making the spacers from thin materials, thereby the amount of material is reduced but this also results in a soft and flexible spacer being difficult to handle while mounting between panes.
U.S. Pat. No. 5,714,214 describes a spacer which minimises both gas diffusion and heat diffusion by combining two spacer parts from material having different properties. In U.S. Pat. No. 5,714,214, two spacer parts are connected at the top with welding points positioned at the top between two folded overlaps. This is a complex solution to manufacture, both because it is a complex task to combine the two spacer parts and obtain the side overlaps, also because a welding means has to access the space between the two overlap parts for welding the welding points, and finally the subsequent bending of the spacer into a desired frame shape will deform the spacer in a manner which may weaken the weldings.